SCR catalyst composition and SCR catalytic article comprising the catalyst composition

Abstract

Disclosed is a catalyst composition for selective catalytic reduction of nitrogen oxides, consisting of at least one vanadium oxide in an amount of 2.0 to 4.0 wt.-%, calculated as V2O5 and based on the total weight of the catalyst composition; at least one tungsten oxide in an amount of 2.5 to 7.2 wt.-%, calculated as WO3 and based on the total weight of the catalyst composition; at least one antimony oxide in an amount of 0.6 to 3.4 wt.-%, calculated as Sb2O5 and based on the total weight of the catalyst composition; at least one zirconium oxide in an amount of 0 to 1.0 wt.-%, calculated as ZrO2 and based on the total weight of the catalyst; and at least one titanium oxide in an amount of 84.6 to 94.9 wt.-%, calculated as TiO2 and based on the total weight of the catalyst, wherein the weight ratio of the oxides of vanadium, tungsten, antimony, titanium and optionally zirconium, calculated as V2O5, WO3, Sb2O5, TiO2 and optionally ZrO2, respectively, add up to 100 wt.-%. Furthermore, disclosed is an SCR catalytic article, wherein the SCR catalyst composition according to the invention is attached in the form of a coating. Suitable catalyst carriers are corrugated substrates and cordierite monoliths. The SCR catalytic articles can be used in a method for reducing nitrogen oxides in the exhaust gas of lean-burn internal combustion engines, and they can also be included in exhaust gas purification systems for treating diesel engine exhaust gas.

Description

[0001] manual

[0002] This invention relates to SCR catalyst compositions composed of oxides of titanium, vanadium, tungsten, antimony, and optionally zirconium. Furthermore, SCR catalytic articles comprising said catalyst compositions are disclosed. The SCR catalyst compositions and SCR catalytic articles comprising said SCR catalyst compositions according to the invention can be used for exhaust gas purification in lean-burn engines, particularly diesel engines.

[0003] The exhaust gases from motor vehicles equipped with internal combustion engines that operate primarily in lean-burn mode specifically contain, in addition to particulate matter, the main emissions: carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides. Because the oxygen content is relatively high, at most 15% by volume, carbon monoxide and hydrocarbons can be relatively easily rendered harmless by oxidation; however, reducing nitrogen oxides to nitrogen is much more difficult.

[0004] Used to remove nitrogen oxides (NOx) from exhaust gases in the presence of oxygen. x One known method is the selective catalytic reduction (SCR) method using ammonia over a suitable catalyst. In this method, ammonia is used to convert the nitrogen oxides to be removed from the waste gas into nitrogen and water. Nitric oxide (NO) and nitrogen dioxide (NO2) are collectively referred to as NO. x .

[0005] Selective catalytic reduction (SCR) occurs in the presence of an SCR catalyst according to the following reaction scheme:

[0006] 4 NO + 4 NH3 + O2 → 4 N2 + 6 H2O (1)

[0007] NO + NO2 + 2 NH3 → 2 N2 + 3 H2O (2)6 NO2 + 8 NH3 → 7 N2 + 12 H2O (3)

[0008] 2 NO2 + 4 NH3 + O2 → 3 N2 + 6 H2O (4)

[0009] Reactions 1 and 2 are the main reactions, and each conversion of one mole of NO... x One mole of ammonia is consumed. Reactions 3 and 4 primarily involve NO. x The reaction occurs in a gaseous form, NO2. A catalyst is used to enable the reaction to occur at temperatures between 150°C and 480°C. The most common types of SCR catalysts are based on vanadium oxide as the active compound on a titanium dioxide (TiO2) support system, or on molecular sieves promoted by transition metals. In the latter case, it primarily involves zeolites promoted by copper and / or iron.

[0010] Reaction 1 is called the "standard SCR reaction", reaction 2 is the "fast SCR reaction", and reactions 3 and 4 are "NO2SCR reactions".

[0011] Ammonia, used as a reducing agent, can be generated as a secondary emission in the emission system or obtained in the exhaust system and subsequent hydrolysis by injecting precursors, such as urea, ammonium carbamate, or ammonium formate.

[0012] To carry out the variant of the SCR method mentioned last, a source of reducing agent, an injection device for metering the reducing agent into the exhaust gas as required, and an SCR catalyst arranged in the exhaust gas flow path are required.

[0013] Mixed oxides can be used as SCR catalysts, specifically those based on oxides of titanium dioxide and / or vanadium (such as vanadium pentoxide), and may contain other oxides such as oxides of silicon, molybdenum, manganese, tungsten, and other elements. These catalysts are described in detail in the following documents; see, for example, WO 89 / 03366A1, EP 0345 695 A2, EP 0 385164A2, WO 2011 / 013006 A2, and US2013 / 205743 A1.

[0014] WO 2011 / 011101 A1 discloses a catalyst for the selective catalytic reduction of nitrogen oxides. This catalyst comprises a metal oxide support, vanadium, an active material, and antimony, acting as a catalyst for the reduction of nitrogen oxides and simultaneously promoting higher resistance to sulfur poisoning and low-temperature catalytic activity. The amount of antimony in the catalyst is preferably from 0.5% to 7% by weight, and the amount of vanadium is preferably from 1% to 3% by weight. According to WO 2011 / 011101 A1, mixed metal oxide catalysts containing tungsten oxide improve resistance to sulfur poisoning at low temperatures; however, the use of tungsten oxide significantly increases the price of the catalyst, which should be avoided for economic reasons. Therefore, the catalyst according to the invention does not contain tungsten. However, the mixed metal oxide catalyst according to WO 2011 / 011101 A1 comprises a support, such as titanium oxide, silicates, zirconium oxide, alumina, and mixtures thereof. Preferably, the support (also synonymously referred to as a carrier) is TiO2.

[0015] WO 2011 / 127505 A1 discloses a catalyst composition comprising a vanadate represented by the formula XVO4 / S, wherein XVO4 represents Bi-, Sb-, Ga-, and / or Al-vanadate, optionally mixed with one or more rare earth metal-vanadates, or with one or more transition metal-vanadates, or with one or more transition metal-vanadates and one or more rare earth metal-vanadates, and S is a support containing TiO2, optionally combined with a dopant, and discloses a method for preparing such a catalyst composition. If XVO4 represents SbVO4, it is synthesized by mixing a SbCl3 solution containing 63.9 wt% Sb2O3 with a solution containing NH4VO3. The solid obtained after calcination is characterized by XRD. The support material is preferably a commercially available TiO2 / WO3 / SiO2. The amounts of TiO2, WO3, and SiO2 in the said support material are not given.

[0016] WO 2017 / 101449 A1 discloses a catalyst composition for the selective catalytic reduction of nitrogen oxides, comprising a TiO2 support, a vanadium- and antimony-containing composite oxide (which has a different composition from VSbO4 and V...). 0.92 Sb 0.92 The rutile structure of O4 (as determined by X-ray diffraction (XRD) using CuKα radiation), and optionally, one or more oxides selected from the group consisting of oxides of silicon oxides, vanadium oxides, and antimony oxides; a method for preparing the catalyst composition, the catalyst composition obtained by / that can be obtained by the method, and its use in the selective catalytic reduction of nitrogen oxides. The support material must contain TiO2, but alternatively, it may also consist of TiO2 and SiO2 and WO3, or TiO2 and ZrO2.

[0017] Vanadium and antimony exist as complex oxides with a rutile structure.

[0018] Vanadium (calculated as element V) is present in the catalyst in an amount of 0.5 wt% to 6 wt%, and antimony (calculated as element Sb) is present in an amount of 0.8 wt% to 16 wt%.

[0019] TiO2 is preferably present in the form of anatase. The titanium content, calculated as TiO2, is preferably in the range of 50% to 97.5% by weight, and the silicon content, calculated as elemental Si (if present), is preferably in the range of 0.2% to 9.5% by weight.

[0020] WO 2017 / 101449 A1 does not mention the amount of WO3 and ZrO2 (if they are present). It explicitly mentions that a) TiO2 and SiO2 and WO3 or b) TiO2 and ZrO2 may be support materials, but it does not explicitly mention that all four oxides, i.e., TiO2 and SiO2 and WO3 and ZrO2 should be present in the catalyst composition.

[0021] CN 107 262 086A relates to an SCR (Selective Catalytic Reduction) denitrification catalyst, and more particularly to an SCR (Selective Catalytic Reduction) denitrification catalyst for accelerating the decomposition of ammonium bisulfate from low-temperature flue gas, its preparation method, and its application. This SCR denitrification catalyst uses a composite oxide formed from titanium oxide and transition metal oxides as a support, vanadium oxide as the active component, and tungsten oxide as a co-catalyst. The molar ratio of transition metal elements to titanium elements in the catalyst is (0.1-0.5):1, and the transition metal oxides include one or more of MnO2, Fe2O3, CeO2, ZrO2, Al2O3, SnO2, Nb2O5, and Sb2O5. By adding an appropriate amount of transition metal oxides to the catalyst, an SCR denitrification catalyst for accelerating the low-temperature decomposition of ammonium bisulfate is prepared, and this catalyst accelerates the decomposition of ammonium bisulfate at temperatures below 350°C. In summary, the catalyst according to CN 107 262 086A comprises oxides of titanium, vanadium, and tungsten, and may also comprise transition metal oxides selected from zirconium dioxide and antimony pentoxide. The molar ratio of one or more transition metal elements, such as ZrO2 and Sb2O5 to TiO2, is between 0.1 and 0.5 and 1.

[0022] WO 2018 / 018406 A1 discloses catalysts for NOx removal, more specifically supported catalysts, monolithic selective catalytic reduction (SCR) catalysts, methods for their preparation, and methods for NOx removal. The supported catalyst comprises a support and a catalytically active component supported on the support, the catalytically active component comprising vanadium, antimony, and at least one additional component selected from oxides of silicon, aluminum, and zirconium, preferably silica and / or alumina. The support material may be selected from TiO2, or TiO2 and SiO2, or TiO2 and WO3, or TiO2, SiO2, and WO3. The support is preferably TiO2, present in an amount of 50 wt% to 97.5 wt%. The V content is preferably in the range of 1 wt% to 10 wt%, and the Sb content is in the range of 1 wt% to 20 wt%, calculated as V2O5 and Sb2O5, respectively. ZrO2 and SiO2 may be present in an amount of 0.5 wt% to 20 wt%. None of the examples presented in WO 2018 / 018406 A1 contain all six elements: Ti, W, V, Sb, and Zr. Examples 9 and 10 contain Ti, Si, W, V, and Sb, but not Zr. These Examples 9 and 10 are examples containing only WO3, and their WO3 content is quite high (9 wt% and 10 wt%, respectively). All other examples disclosed in WO 2018 / 018406 A1 contain only some of these five elements. Many examples contain antimony oxide, but in varying amounts. According to the SCR activity comparison conducted in WO 2018 / 018406 A1, a low antimony oxide content of about 2 wt% shows a significantly lower NOx conversion compared to catalysts containing a higher amount of antimony oxide (i.e., from 7 wt% to about 16 wt% antimony oxide). In WO 2018 / 018406 A1, antimony oxide is calculated as Sb₂O₃.

[0023] US2016 / 0288094 A1 discloses a catalyst comprising at least two catalytically active layers A and B. Layer A is applied directly to a support body, and layer B is applied to layer A, covering at least a portion or the entire length of layer A. Thus, layer B is in contact with the exhaust gas before layer A. The support can be a through-hole honeycomb body or a wall-flow filter. Both layers A and B comprise a support oxide selected from titanium dioxide, zirconium dioxide, or alumina, preferably titanium dioxide. Layer A comprises vanadium pentoxide and tungsten trioxide as catalytically active metal oxides, and optionally also comprises silicon dioxide and / or antimony pentoxide. Layer B comprises vanadium pentoxide, tungsten trioxide, and silicon dioxide, and optionally antimony pentoxide. The total weight of layer A is greater than the total weight of layer B, and the proportion of vanadium pentoxide in layer A is greater than the proportion of vanadium pentoxide in layer B. If layer A contains silicon dioxide, its proportion in layer A is less than its proportion in layer B. The catalyst in the example has a high tungsten pentoxide ratio of about 7% to 10% by weight in both layer A and layer B.

[0024] In HH Phil, MP Reddy, PA Kumar, LK Ju, and JS Hyo, “SO2-resistant antimony-promoted NH3-SCR of NOx with V2O5 / TiO2 catalyst at low temperatures,” Applied Catal B 2008, 78, 301-308, the effect of promoters on the sulfur resistance of V2O5 / TiO2 SCR catalysts was investigated. Promoters were selected from Se, Sb, Cu, S, B, Bi, Pb, and P. Selenium exhibited the best NOx conversion between 150 °C and 400 °C, but was excluded due to its high vapor pressure. Among the remaining promoters, 2 wt% Sb loaded on V2O5 / TiO2 showed the best combination of NOx conversion and high resistance to SO2. The catalyst with 2 wt% Sb on V2O5 / TiO2 was compared with a commercially available catalyst containing 10 wt% W on V2O5 / TiO2. Both catalysts exhibited comparable NOx conversion and SO2 resistance, but activity measurements using both catalysts, i.e., in the presence of SO2 and NO, showed differences. x Measurements in atmospheres of NH3, O2, and H2O also revealed significant amounts of ammonium sulfate formation. When tungsten is used as a promoter, the percentage of tungsten needs to be increased to approximately 5% to 10% by weight to achieve resistance to sulfur poisoning at low temperatures. Since the amount of tungsten increases the price of the catalyst, the aim of this study was to discover a promoter that can replace tungsten and improve sulfur poisoning resistance at low temperatures.

[0025] Because internal combustion engines in motor vehicles operate on transient driving cycles, SCR catalysts must ensure the highest possible NOx conversion with good selectivity, even under a wide range of operating conditions. Therefore, complete and selective conversion of the amount of NOx that occurs should be ensured at low temperatures, just as it is at high temperatures, such as when the throttle is fully open.

[0026] However, previous technologies could not simultaneously optimize vanadium SCR catalysts in two aspects: low-temperature activity (T < 250 °C) and thermal stability, and the activity of fresh and aged catalysts. Improvements in low-temperature activity are always related to deficiencies in thermal stability, and vice versa, and with necessary corrections, this also applies to the activity of fresh catalysts relative to aged catalysts.

[0027] The problem to be solved by the present invention

[0028] However, the market demand for such catalyst compositions is increasing daily. Therefore, an object of the present invention is to provide a vanadium-containing catalyst composition for the selective catalytic reduction of nitrogen oxides, which exhibits good low-temperature activity, better thermal stability, and good catalytic performance in both fresh and aged conditions. Another object of the present invention is to provide an SCR catalytic product comprising the aforementioned SCR catalyst composition.

[0029] Solution to the problem

[0030] The purpose of providing a vanadium-containing catalyst composition for the selective catalytic reduction of nitrogen oxides is achieved by a catalyst composition characterized by good low-temperature activity, while exhibiting greater high-temperature selectivity, and demonstrating good catalytic performance in both fresh and aged conditions. This catalyst composition comprises the following:

[0031] At least one vanadium oxide in an amount of -2.0% to 4.0% by weight, calculated as V₂O₅ and based on the total weight of the catalyst composition.

[0032] -2.5% to 7.2% by weight of at least one tungsten oxide, calculated as WO3 and based on the total weight of the catalyst composition.

[0033] At least one antimony oxide in an amount of -0.6% to 3.4% by weight, calculated as Sb₂O₅ and based on the total weight of the catalyst composition.

[0034] At least one zirconium oxide in an amount of -0% to 1.0% by weight, calculated as ZrO2 and based on the total weight of the catalyst.

[0035] - and at least one titanium oxide in an amount of 84.6% to 94.9% by weight, calculated as TiO2 and based on the total weight of the catalyst,

[0036] The total weight ratio of the oxides of vanadium, tungsten, antimony, titanium and zirconium, calculated as V2O5, WO3, Sb2O5, TiO2 and optionally ZrO2, reaches 100 by weight.

[0037] Surprisingly, the novel catalyst composition exhibits good activity at both low and high temperatures, and also shows better thermal stability in both fresh and aged conditions.

[0038] The following explains the catalyst composition for selective catalytic reduction of nitrogen oxides according to the present invention and the SCR catalytic product comprising the said SCR catalyst composition, which exhibits good low-temperature activity while having greater high-temperature selectivity and good catalytic performance in both fresh and aged states. The present invention includes all the embodiments individually and in combination below.

[0039] A “catalyst composition” is a substance or mixture of substances capable of converting one or more components of exhaust gas into one or more other components. Therefore, a “catalyst composition” is catalytically active. Examples of such catalyst compositions are, for example, oxidation catalyst compositions capable of converting volatile organic compounds and carbon monoxide into carbon dioxide or ammonia into nitrogen oxides. Another example of such catalysts is, for example, a selective reduction catalyst (SCR) composition capable of converting nitrogen oxides into nitrogen and water. In the context of this invention, an SCR catalyst is a catalyst comprising a support substrate and an SCR catalyst composition. The SCR catalyst composition according to the invention comprises at least one catalytically active metal oxide of each of vanadium, tungsten, antimony, and titanium as defined above, and optionally zirconium.

[0040] A "catalyst substrate" (also simply "support substrate") is a support on which a catalyst composition is attached and to which the final catalyst is shaped. Therefore, a support substrate is a carrier used for catalytically active compositions.

[0041] Suspensions and dispersions are heterogeneous mixtures containing solid particles and solvent. The solid particles do not dissolve but are suspended in the solvent, floating freely in the medium. If the solid particles have an average particle size of 1 μm or less, the mixture is called a dispersion; if the average particle size is greater than 1 μm, the mixture is called a suspension.

[0042] In the context of this invention, the term "mixture" refers to a material composed of two or more different substances that are physically combined, and in which each component retains its own chemical properties and composition. Although its composition does not undergo chemical change, the physical properties of a mixture (such as its melting point) may differ from the physical properties of its components.

[0043] "Repair substrate coating" is a suspension or dispersion of solid particles that can be applied to a catalyst substrate. This suspension or dispersion is often referred to as a "repair substrate coating slurry." The slurry is applied to a carrier substrate and then dried.

[0044] Two or more repair base coats can also be applied sequentially to a carrier substrate. Those skilled in the art will understand that two or more repair base coats can be applied to a single carrier substrate in a “layered” or “partitioned” manner, and layering and partitioning can also be combined. In the layered case, the repair base coats are applied sequentially to the carrier substrate. The repair base coat applied first and thus in direct contact with the carrier substrate represents the “bottom layer,” and the last applied repair base coat represents the “top layer.” In the partitioned case, the first repair base coat is applied to the carrier substrate from a first front side A towards another front side B, but not along the entire length of the carrier substrate; rather, it is applied only to the endpoint between front side A and front side B. Then, the second repair base coat is applied to the carrier, starting from front side B and continuing to the endpoint between front side B and front side A. The endpoints of the first and second repair base coats do not need to be the same: if they are the same, the two repair base coat areas are adjacent to each other. However, if the endpoints of the two repair base coating areas located between front surfaces A and B of the carrier substrate are not identical, a gap may exist between the first and second repair base coating areas, or they may overlap. As described above, layering and partitioning can also be combined if, for example, one repair base coating is applied over the entire length of the carrier substrate, and the other repair base coating is applied only from one front surface to the endpoint between the two front surfaces.

[0045] The repair substrate coating of this invention comprises a solvent (typically water) and particles of at least one titanium oxide. Furthermore, the repair substrate coating may optionally contain a binder and / or additives. Suitable binders are, for example, alumina, silica, non-zeolite silica-alumina, and naturally occurring clays. Suitable additives are, for example, polyacrylates, amines, citrates, tartrates, and rheology modifiers such as starch and cellulose. Such binders and additives are known to those skilled in the art and can be used in the context of this invention without departing from the scope of the claims.

[0046] Repair base coatings can be applied to the carrier substrate in one or more steps.

[0047] In one embodiment of the invention, the repair substrate coating slurry comprises a solvent (typically water) and particles of at least one titanium oxide. The repair substrate coating is applied to a substrate and dried. Subsequently, for example, each of the at least one oxide of vanadium, tungsten, antimony, and optionally zirconium, or its precursor, is applied to the dried and calcined repair substrate coating by impregnating the dried and calcined repair substrate coating with a precursor of each of the at least one oxides of vanadium, tungsten, antimony, and optionally zirconium. Each of the at least one oxides of vanadium, tungsten, antimony, and zirconium may be applied in the form of a precursor of the oxide, or all of them may be applied in the form of oxides, or some oxides may be applied in the form of a precursor of an oxide and some oxides may be applied in the form of oxides.

[0048] The precursor is a chemical compound of a metal containing a desired oxide of vanadium, tungsten, antimony, or zirconium, such as a salt, which can be converted into the final oxide, for example, by heat treatment.

[0049] In another embodiment of the invention, the repair substrate coating slurry comprises a solvent (typically water), at least one titanium oxide, and each of at least one oxide of vanadium, tungsten, antimony, and optionally zirconium, and / or a precursor of at least one oxide of vanadium, tungsten, antimony, and optionally zirconium. When using precursors of at least one oxide of vanadium, tungsten, antimony, and optionally zirconium, these are subsequently converted into catalytically active metal oxides as described above.

[0050] At least one titanium oxide and some oxides of vanadium, tungsten, antimony, and optionally zirconium, and / or their precursors, can also be applied to the catalyst substrate in the form of a repair substrate coating slurry, and subsequently, other oxides of vanadium, tungsten, antimony, and optionally zirconium are applied, for example, by impregnation as described above, onto the dried and calcined repair substrate coating. In the context of this invention, a "coating" is an SCR catalyst composition according to the invention that has been adhered to the catalyst substrate. The fixation of the SCR catalyst composition can be carried out according to the embodiments described above. Thus, the coating comprises oxides of titanium, vanadium, tungsten, antimony, and optionally zirconium as described above.

[0051] In embodiments of the invention where the repair substrate coating comprises all metal oxides of a catalyst composition or its precursor, the repair substrate coating is dried, for example, at room temperature after being applied to a carrier substrate. Subsequently, the coated carrier substrate is calcined, for example, at a temperature of 500°C to 600°C. This method of applying the repair substrate coating to the substrate is referred to below as the "one-pot method". Corrugated substrates and cordierite substrates are both feasible.

[0052] In some, but not all, embodiments of the invention in which the repair substrate coating comprises a metal oxide of a catalyst composition or its precursor, the repair substrate coating is dried, for example, at room temperature after being applied to a carrier substrate. Subsequently, the coated carrier substrate is calcined, for example, at a temperature of 500°C to 600°C. Then, other oxides or their precursors are applied, for example, by impregnation, to the dried repair substrate coating, followed by a drying step, preferably at room temperature. The coated carrier substrate is then heated to a temperature of 450°C to 600°C. If a metal oxide precursor has been used, this heating step decomposes the precursor into the corresponding metal oxide.

[0053] These methods for applying, drying, and calcining repair coatings and for decomposing metal oxide precursors to convert them into the corresponding metal oxides are well known to those skilled in the art and can be applied in the context of this invention without departing from the scope of the claims.

[0054] Optionally, the catalyst support material can be mixed with each of at least one oxide of titanium, vanadium, tungsten, antimony, and optionally zirconium, or a precursor thereof, and then extruded. Alternatively, only the catalyst support material and at least one titanium oxide can be extruded, followed by the application of other oxides or precursors thereof. Furthermore, the catalyst support material, at least one titanium oxide, and some other oxides or precursors thereof can be extruded, followed by the application of other oxides or precursors thereof. Such extrusion methods are known to those skilled in the art and can be applied in the context of this invention without departing from the scope of the claims.

[0055] A “catalytic product” or “brick” contains a catalyst substrate and a coating attached thereto.

[0056] In the context of this invention, "SCR catalyst loading" refers to the concentration of the SCR catalyst composition, expressed in grams of each component per liter of catalyst substrate.

[0057] "SCR catalyst products" are suitable for removing NO from waste gas or exhaust gases. x Catalysts.

[0058] In the context of this invention, a "system" for purifying exhaust gases includes two or more catalytic articles arranged in a row, wherein each individual catalytic article is designed to remove a specific component of the exhaust gas, such as volatile organic compounds (VOCs), hydrocarbons (HC), and carbon monoxide in the case of an oxidation catalyst, nitrogen oxides in the case of an SCR catalyst, particulate matter in the case of a particulate filter, or excess ammonia in the case of an ammonia leak catalyst (ASC). These catalytic articles are well known.

[0059] "Upstream" and "downstream" are terms relative to the normal flow direction of exhaust gas in the exhaust pipe. "A zone or catalyst 1 located upstream of zone or catalyst 2" means that zone or catalyst 1 is positioned closer to the exhaust gas source, i.e., closer to the combustion source, such as the motor, than zone or catalyst 2. The flow direction is from the exhaust gas source, i.e., from the combustion source, to the exhaust pipe. Therefore, according to this flow direction, exhaust gas enters each zone or catalyst at its inlet end and exits each zone or catalyst at its outlet end.

[0060] Depending on the amount of oxides of vanadium, tungsten, antimony, and optionally zirconium, the at least one titanium oxide is present in an amount of 84.6% to 94.9% by weight. This means that oxides of vanadium, tungsten, antimony, and optionally zirconium are present within the ranges given above, and the remainder is titanium oxide, such that the total amount of all oxides adds up to 100% by weight. The at least one titanium oxide is titanium dioxide (TiO2). TiO2 is known to exist in several phases, including anatase, rutile, and brookite. Suitable titanium dioxide comprises at least 95% by weight of anatase, preferably at least 98% by weight, and even more preferably at least 99.5% by weight. The remainder, bringing the total to 100% by weight, is preferably represented by rutile and / or brookite, more preferably by rutile.

[0061] At least one vanadium oxide is present in an amount of 2.0% to 4.0% by weight, preferably 2.4% to 3.4% by weight, more preferably 2.4% to 2.8% by weight. In one embodiment, the at least one vanadium oxide is vanadium pentoxide (V₂O₅).

[0062] At least one tungsten oxide is present in an amount of 2.5% to 7.2% by weight, preferably 2.5% to 7.0% by weight, even more preferably 3.0% to 5.5% by weight, and most preferably 3.5% to 5.0% by weight. In one embodiment, at least one tungsten oxide is tungsten trioxide (WO3).

[0063] At least one antimony oxide is present in an amount of 0.6% to 3.4% by weight, preferably 1.5% to 2.5% by weight. In one embodiment, at least one antimony oxide is present in the form of antimony pentoxide (Sb₂O₅).

[0064] The catalyst composition according to the invention comprises at least one zirconium oxide in an amount of 0% to 1.0% by weight. This means that there is no zirconium oxide, corresponding to an amount of 0% by weight of at least one zirconium oxide, or that at least one zirconium oxide is present in an amount greater than 0% to 1.0% by weight. The term "optionally zirconium" as used in this invention includes embodiments in which zirconium oxide is absent, and embodiments in which at least one zirconium oxide is contained in an amount greater than 0% to 1.0% by weight.

[0065] In embodiments containing zirconium, zirconium is present in an amount greater than 0 wt% to 1.0 wt%, preferably 0.01 wt% to 1.0 wt%, more preferably 0.2 wt% to 1.0 wt%, and even more preferably 0.4 wt% to 0.7 wt%. In one embodiment, at least one zirconium oxide is zirconium dioxide (ZrO2).

[0066] The preferred amounts of oxides of titanium, tungsten, vanadium, and antimony are the same as those given above for catalysts that do not contain zirconium, and this also applies to the properties of the preferred oxides of these elements.

[0067] Those skilled in the art know that vanadium, tungsten, antimony, and zirconium each form several oxides, in which the metals have different oxidation states.

[0068] Known vanadium oxides include, for example, V₂O₃, VO₂, and V₂O₅.

[0069] Known tungsten oxides include, for example, WO2 and WO3.

[0070] Known antimony oxides include, for example, Sb₂O₃, Sb₂O₄, and Sb₂O₅.

[0071] Known zirconium oxides include, for example, ZrO2.

[0072] Those skilled in the art know that oxides of these metals in various oxidation states can coexist, and some metals, particularly vanadium, form a wide range of oxide families. However, in the context of this invention, the amounts of vanadium, tungsten, antimony, and zirconium oxides are calculated in the form of oxides V₂O₅, WO₃, Sb₂O₅, and ZrO₂. Those skilled in the art know how to determine the amounts of the corresponding metals vanadium, tungsten, antimony, and zirconium in a catalyst composition and how to convert them into amounts of V₂O₅, WO₃, Sb₂O₅, and ZrO₂.

[0073] In one embodiment of the present invention, the catalyst composition for the selective catalytic reduction of nitrogen oxides comprises the following:

[0074] At least one vanadium oxide in an amount of -2.0% to 4.0% by weight, calculated as V₂O₅ and based on the total weight of the catalyst composition.

[0075] -2.5% to 7.2% by weight of at least one tungsten oxide, calculated as WO3 and based on the total weight of the catalyst composition.

[0076] At least one antimony oxide in an amount of -0.6% to 3.4% by weight, calculated as Sb₂O₅ and based on the total weight of the catalyst composition.

[0077] - and at least one titanium oxide in an amount of 85.6% to 94.9% by weight, calculated as TiO2 and based on the total weight of the catalyst,

[0078] The total weight ratio of the oxides of vanadium, tungsten, antimony and titanium, calculated as V2O5, WO3, Sb2O5 and TiO2 respectively, reaches 100 by weight.

[0079] In another embodiment of the invention, the catalyst composition for the selective catalytic reduction of nitrogen oxides comprises the following:

[0080] At least one vanadium oxide in an amount of -2.0% to 4.0% by weight, calculated as V₂O₅ and based on the total weight of the catalyst composition.

[0081] -2.5% to 7.2% by weight of at least one tungsten oxide, calculated as WO3 and based on the total weight of the catalyst composition.

[0082] At least one antimony oxide in an amount of -0.6% to 3.4% by weight, calculated as Sb₂O₅ and based on the total weight of the catalyst composition.

[0083] At least one zirconium oxide in an amount of -0.2 wt% to 1.0 wt%, calculated as ZrO2 and based on the total weight of the catalyst.

[0084] - and at least one titanium oxide in an amount of 84.6% to 94.7% by weight, calculated as TiO2 and based on the total weight of the catalyst,

[0085] The total weight ratio of the oxides of vanadium, tungsten, antimony, titanium and zirconium, calculated as V2O5, WO3, Sb2O5, TiO2 and ZrO2 respectively, reaches 100 by weight.

[0086] The SCR catalytic article according to the present invention comprises a catalyst substrate, and the SCR catalyst composition according to the present invention is attached to the catalyst substrate in the form of a coating.

[0087] The catalyst substrate is selected from corrugated substrate and cordierite solid material.

[0088] Suitable cordierite monoliths can be used as wall-flow filters or flow-through substrates. Wall-flow filters or flow-through substrates can exist in the form of honeycomb structures.

[0089] In one embodiment, the carrier substrate is a corrugated substrate, also referred to below as a "monolithic corrugated substrate". Such monolithic corrugated substrates are well known to those skilled in the art. They are disclosed, for example, in WO 2010 / 066345 A1. The corrugated substrate preferably has a wall density of at least 50 g / l but not more than 300 g / l and a porosity of at least 50%. The monolithic substrate is cellophane or E-glass fiber paper with a high silica content. Optionally, the paper has a diatomaceous earth layer and / or a titanium dioxide layer. Diatomaceous earth is a naturally occurring, soft siliceous sedimentary rock that is easily broken into a fine white to off-white powder. Siliceous rocks are sedimentary rocks with silica (SiO2) as their main component.

[0090] The catalytic product in which the catalyst composition is applied to a corrugated substrate has the following advantages: the catalytic layer, i.e., the layer formed by applying the catalyst composition to the support substrate, does not peel off from the monolithic substrate during the start-up and shutdown of the internal combustion engine or gas turbine. Furthermore, the catalyst has been shown to have improved catalytic activity.

[0091] The catalytic material is applied to a monolithic substrate, which may be in the form of a flat or corrugated plate. The substrate is made of E-glass fiber sheets or glass sheets with a high silicon content. Optionally, these sheets may contain a TiO2 layer, a diatomaceous earth layer, or a layer containing both TiO2 and diatomaceous earth.

[0092] High-silicon glass contains 94 to 95 wt% SiO2, 4 to 5 wt% Al2O3, and some Na2O. These fibers have a density of 2000 g / L to 2200 g / L and a fiber diameter of 8 μm to 10 μm. An example is commercially available SILEX short fibers.

[0093] E-glass contains 52% to 56% SiO2, 12% to 16% Al2O3, 5% to 10% B2O3, 0% to 1.5% TiO2, 0% to 5% MgO, 16% to 25% CaO, 0% to 2% K2O / Na2O, and 0% to 0.8% Fe2O3.

[0094] Preferably, the substrate material is selected such that the density of the substrate is at least 50 g / L but not more than 300 g / L, and the porosity of the substrate wall is at least 50% of the material volume.

[0095] The porosity of the monolithic substrate is obtained through pores with depths of 50 μm to 200 μm and diameters of 1 μm to 30 μm.

[0096] The preferred amounts of oxides of titanium, tungsten, antimony, and optionally zirconium are the same as those given above for catalyst compositions containing or not containing zirconium, and this also applies to the properties of the preferred oxides of these elements.

[0097] The SCR catalyst composition is fixed onto the catalyst substrate in the form of a coating by applying a repair substrate coating as defined above to the catalyst substrate.

[0098] The repair substrate coating comprises at least one solvent, preferably water, and at least one titanium oxide particle. The at least one titanium oxide is preferably TiO2, and it comprises at least 95% by weight, preferably at least 98% by weight, and even more preferably at least 99.5% by weight of anatase. The remaining portion, totaling 100% by weight, is preferably represented by rutile and / or brookite, more preferably by rutile.

[0099] In one embodiment, the repair substrate coating further comprises a binder, such as alumina, silica, non-zeolite silica-alumina, or naturally occurring clay.

[0100] In another embodiment, the repair substrate coating further comprises additives such as polyacrylates, amines, citrates, tartrates, and rheology modifiers such as starch and cellulose.

[0101] In yet another implementation, the repair substrate coating additionally contains additives but no binder.

[0102] Where the coating should contain at least one zirconium oxide, zirconium dioxide or its precursor may be added to the repair substrate coating.

[0103] Adhesives and / or additives and / or at least one zirconium oxide or its precursor may also be added to the repair substrate coating.

[0104] In one embodiment, the repair substrate coating consists of water, titanium dioxide, and optionally a binder and / or additives and / or at least one zirconium oxide or its precursor.

[0105] In another embodiment, the repair substrate coating consists of water, titanium dioxide and a precursor of each of at least one oxide of vanadium, tungsten, antimony and optionally zirconium, and / or at least one oxide of vanadium, tungsten, antimony and optionally zirconium, as well as an optional binder and / or additives.

[0106] In yet another embodiment, the repair substrate coating consists of water, titanium dioxide, and oxides and / or precursors of vanadium, tungsten, antimony, and optionally zirconium, as well as binders and / or additives.

[0107] The repair substrate coating is applied to the catalyst substrate in a direction perpendicular to the front surfaces A and B of the catalyst substrate. It can be applied from top to bottom, preferably by applying the repair substrate coating under pressure in a direction from the top side to the bottom side. Alternatively, the repair substrate coating can be applied from bottom to top, preferably by immersing it under reduced pressure from the bottom side to the top side. Applying the repair substrate coating from top to bottom and from bottom to top is well known to those skilled in the art, and this knowledge can be applied in the context of the invention without departing from the scope of the claims.

[0108] The dry matter and pH of the repair substrate coating can be easily adjusted to achieve the desired coating load. In embodiments of the invention, the pH of the repair substrate coating is adjusted to be different from the isoelectric point (IEP) of the particles suspended or dispersed in the repair substrate coating. The isoelectric point is the pH value at which the particles do not carry a net charge. A pH value stronger than the IEP can be adjusted by adding an acid (e.g., nitric acid). A pH value stronger than the IEP can be adjusted by adding a base (e.g., ammonia or amine). Those skilled in the art know how to adjust the dry matter and pH of the repair substrate coating and can apply this knowledge without departing from the scope of the claims.

[0109] Optionally, the repair base coating may be ground, for example, in a bead mill, before being applied to the catalyst substrate. Preferably, the particles contained in the repair base coating may be ground to a D90 particle size of ≤2 μm.

[0110] Subsequently, the repair substrate coating is dried and calcined after being applied to the catalyst substrate, for example, dried at room temperature and then calcined at 500°C to 600°C.

[0111] If the repair substrate coating does not contain oxides of all vanadium, tungsten, antimony, and optionally zirconium, the oxides not yet applied may be applied in subsequent steps, for example, by impregnating the repair substrate coating with these oxides and / or their precursors. Impregnation may be performed, for example, by immersing the catalyst substrate coated with the repair substrate coating in an aqueous solution of the precursor. Precursors of vanadium, tungsten, antimony, and zirconium oxides are preferably used in the form of their aqueous solutions.

[0112] Suitable vanadium precursor salts are ammonium metavanadate and vanadium oxalate and tartrate.

[0113] A suitable tungsten precursor salt is ammonium metatungstate.

[0114] Suitable antimony precursor salts are antimony sulfate, antimony acetate, antimony tartrate, antimony glycolate, and antimony acetylacetone.

[0115] Suitable zirconium precursors are zirconium chloride (IV), zirconium oxynitrate (IV), and zirconium oxysulfate (IV).

[0116] If an antimony precursor other than antimony tartrate is used, tartaric acid is preferably added to an aqueous solution of the antimony precursor. Preferably, tartaric acid and the antimony precursor are used in a molar ratio of tartaric acid to antimony of 2:1 to 8:1.

[0117] In one embodiment of the invention, the catalyst substrate is a corrugated substrate, and the repair substrate coating consists of water, titanium dioxide, and optionally a binder and / or additives and / or at least one zirconium oxide or its precursor. If the catalyst composition according to the invention is to contain zirconium, then the zirconium precursor is most preferably added to the repair substrate coating. After the repair substrate coating is applied, the corrugated substrate coated with the repair substrate coating is then impregnated with an aqueous solution of vanadium, tungsten, and antimony precursors. The application, drying, and calcination of the repair substrate coating, as well as the decomposition of the metal oxide precursors into the corresponding metal oxides, are performed as described above.

[0118] In another embodiment of the invention, the catalyst substrate is a corrugated substrate, and the repair substrate coating comprises titanium dioxide and oxides of vanadium, tungsten, and antimony, and / or precursors of vanadium, tungsten, and antimony, and optionally a binder and / or additives and / or at least one zirconium oxide or its precursor. Again, the application, drying, and calcination of the repair substrate coating, as well as the decomposition of the metal oxide precursor into the corresponding metal oxide, are performed as described above. This method of applying the repair substrate coating is the "one-pot method" as defined above.

[0119] In another embodiment of the invention, the catalyst substrate is a cordierite substrate as described above, and the repair substrate coating comprises titanium dioxide and oxides of vanadium, tungsten, and antimony, as well as optionally a binder and / or additives and / or at least one zirconium oxide or its precursor.

[0120] If a repair substrate coating comprising the catalyst composition according to the invention is to be applied to a corrugated substrate, the repair substrate coating is preferably between 250 g / L and 550 g / L, more preferably between 350 g / L and 450 g / L.

[0121] If a repair substrate coating comprising the catalyst composition according to the invention is to be applied to a cordierite substrate, the repair substrate coating is preferably between 100 g / L and 500 g / L, more preferably between 150 g / L and 400 g / L.

[0122] The catalytic product according to the invention is particularly suitable for reducing nitrogen oxides in the exhaust gas of lean-burn internal combustion engines (specifically, diesel engines).

[0123] Therefore, the present invention also relates to a method for reducing nitrogen oxides in the exhaust gas of a lean-burn internal combustion engine, the method comprising the following steps:

[0124] - Add a reducing agent to the exhaust gas containing nitrogen oxides, and

[0125] - The resulting mixture from waste gas containing nitrogen oxides and a reducing agent is passed through a catalytic product according to the invention.

[0126] As a reducing agent, ammonia is particularly considered due to its specific advantages. Instead of ammonia itself, ammonia precursors (specifically, urea) are added to the exhaust gas containing nitrogen oxides.

[0127] Specifically, the catalyst according to the invention is used as a component of an exhaust gas cleaning system, which, in addition to the catalytic article according to the invention, also includes, for example, an oxidation catalyst and a diesel particulate filter disposed on the inflow side. Thus, the catalytic article according to the invention can also be present as a coating on the diesel particulate filter.

[0128] Therefore, the present invention also relates to an exhaust gas purification system for treating diesel engine exhaust gas, the exhaust gas purification system comprising, in the direction of exhaust gas flow:

[0129] -Oxidation catalyst,

[0130] - Diesel engine particulate filter, and

[0131] -According to the catalyst product of the present invention,

[0132] or

[0133] -Oxidation catalyst, and

[0134] - A diesel particulate filter, wherein the catalyst composition according to the invention is present as a coating on the diesel particulate filter.

[0135] The oxidation catalysts (particularly platinum, palladium, or platinum and palladium supported on, for example, alumina) and diesel particulate filters suitable for the exhaust gas purification systems according to the present invention are known to those skilled in the art and are commercially available.

[0136] The waste gas purification system according to the invention typically includes a device for metering the reducing agent, which is arranged upstream of the catalyst according to the invention. The injection device can be selected by those skilled in the art. Such devices are well known to those skilled in the art, and they can be used in the context of the invention without departing from the scope of the claims.

[0137] The reducing agent introduced into the exhaust gas stream via the injection device can be, in particular, ammonia itself or in the form of a compound from which ammonia is formed under ambient conditions. Examples of suitable compounds are aqueous solutions of urea or ammonium formate, as well as solid ammonium carbamate. Generally, the reducing agent or its precursor is contained in a container attached to and connected to the injection device. Attached Figure Description

[0138] Figure 1 The figure shows the NO content (in weight%) in a catalyst composition containing 3.6 wt% WO3 and 1.6 wt% Sb2O5, compared to a catalyst containing 2.7 wt% V2O5, 4.0 wt% WO3, and 0 wt% Sb2O5, at 200°C under both fresh and aged conditions, varying with the amount of V2O5 (wt%). x Transformation.

[0139] Figure 2 The formation of N2O in a catalyst composition containing 3.6 wt% WO3 and 1.6 wt% Sb2O5, in both fresh and aged conditions at 550 °C, is shown to vary with the amount of V2O5 (in wt%) compared to a catalyst containing 2.7 wt% V2O5, 4.0 wt% WO3 and 0 wt% Sb2O5.

[0140] Figure 3 The figure shows the NO content (in weight%) of a catalyst composition containing 2.4% V2O5 and 1.6% Sb2O5, varying with the amount of WO3 at 200°C in both fresh and aged conditions, compared to a catalyst containing 2.7% V2O5 and 0% Sb2O5. x Transformation.

[0141] Figure 4 The formation of N2O in a catalyst composition containing 2.4 wt% V2O5 and 1.6 wt% Sb2O5 at 550 °C under fresh and aged conditions is shown to vary with the amount of WO3 (in wt%) compared to a catalyst containing 2.7 wt% V2O5 and 0 wt% Sb2O5.

[0142] Figure 5 The figure shows the NO variation with respect to the amount of Sb₂O₅ for a fresh catalyst composition. x Transformation.

[0143] Figure 6 The figure shows the NO content as a function of the amount of Sb₂O₅ for the aged catalyst composition. x Transformation.

[0144] Figure 7 The NOx conversion and N2O formation at 550 °C are shown for a sample containing 0% by weight ZrO2.

[0145] Figure 8 This shows the NO content at 550°C for a sample prepared using the one-pot method. x Transformation and N2O formation.

[0146] Implementation Plan

[0147] Implementation Scheme 1: Preparation of SCR catalyst products with corrugated catalyst substrate

[0148] The SCR catalyst article according to the present invention is prepared. A corrugated substrate is used as the catalyst substrate, and the SCR catalyst composition according to the present invention and some comparative catalyst compositions are attached thereto.

[0149] Preparation of catalytic products with corrugated catalyst substrate

[0150] A water-based slurry containing TiO2 (anatase) and ZrO(NO3)2 with a dry matter content of 57% to 59% was applied to a corrugated substrate with a cpsi of 260, where “cpsi” means “pores per square inch”. The substrate was then calcined at 580 °C. Subsequently, an impregnation solution was prepared by mixing A grams of an water-based solution containing vanadium oxalate (7.15% V), B grams of an aqueous solution of ammonium metatungstate (39.36% W), C grams of deionized water, D grams of tartaric acid, and E grams of antimony acetate (Sb(OAc)3) in different amounts (see Table 1). The substrate was then immersed in the impregnation solution for 20 seconds, dried, and then heat-treated at 450 °C to produce catalytic loadings of % V2O5, % WO3, % Sb2O5, and % ZrO2 based on the total weight of the catalyst composition, as shown in Table 1.

[0151] Table 1: Preparation of catalytic products with corrugated catalyst substrates and the V2O5, WO3 and... of the obtained catalytic products Sb2O5 content

[0152]

[0153] It should be noted that Examples 1, 4, 7, 8 and 9 in Table 1 are comparative examples because they do not contain tungsten or antimony, or neither tungsten nor antimony.

[0154] Implementation Scheme 2: NOx Conversion and N2O Formation of SCR Catalysts with Corrugated Catalyst Substrates

[0155] NOx conversion and N2O formation were tested in the fresh state and after aging under the following conditions, according to the embodiment of implementation 1:

[0156] NOx (250ppm), NH3 (300ppm), H2O (4%), O2 (12%), GSVH=100,000h -1 The remaining N2. NOx conversion was measured at 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ and 550℃.

[0157] At 550℃, H2O = (10%), and GSVH = 10,000 h -1 After 100 hours of aging.

[0158] All percentages given above refer to volume percentages.

[0159] GHSV is the air velocity.

[0160] Based on inlet and outlet NO x Concentration, NO x The calculation is transformed as follows:

[0161]

[0162] in

[0163] X: NO in percentage terms x Transformation

[0164] NOx in NO at the inlet end of SCR catalyst products x concentration

[0165] NOx out NO at the outlet of SCR catalyst products x concentration

[0166] NO at the inlet and outlet x Concentration can be expressed in mol or by mass. NO is measured by FTIR. x And the concentration of N2O.

[0167] The results of NOx conversion and N2O formation in the fresh and aged examples are shown in Tables 2 and 3.

[0168] X(T) represents NO at temperature T in °C. x Transformation. The formation of N2O was measured at 550℃.

[0169] Table 2: NO at 550°C for Fresh Examples 1 to 26 x Conversion and N2O formation

[0170]

[0171]

[0172] Table 3: NO at 550°C for Aging Examples 1 to 26 x Conversion and N2O formation

[0173]

[0174] Implementation Plan 3: NO based on changes in V2O5 x Conversion and N2O formation

[0175] In a catalyst composition containing 3.6 wt% WO3 and 1.6 wt% Sb2O5, the NO content varies with the amount of V2O5 (in wt%) at 200°C under fresh and aged conditions. x Transformation shown in Figure 1For comparison, a catalyst comprising 2.7 wt% V₂O₅, 4.0 wt% WO₃, and 0 wt% Sb₂O₅ is also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance of 100 wt% is represented by TiO₂.

[0176] The aging of the catalyst composition and the measurement of NOx conversion were performed as described above.

[0177] Table 4 lists the catalyst compositions and NOx conversion.

[0178] The result is Figure 1 As shown in the image.

[0179] Table 4: Compared with catalysts containing 2.7 wt% V₂O₅, 4.0 wt% WO₃ and 0 wt% Sb₂O₅, in In a catalyst composition containing 3.6 wt% WO3 and 1.6 wt% Sb2O5, under fresh and aged conditions at 200°C NO varies according to the amount of V2O5 (in weight %) x Transformation .

[0180]

[0181] In a catalyst composition comprising 3.6 wt% WO3 and 1.6 wt% Sb2O5, the formation of N2O at 550°C under fresh and aged conditions, varying with the amount of V2O5 (in wt%), is shown below. Figure 2 For comparison, a catalyst comprising 2.7 wt% V₂O₅, 4.0 wt% WO₃, and 0 wt% Sb₂O₅ is also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance of 100 wt% is represented by TiO₂.

[0182] The aging of the catalyst composition and the measurement of N2O formation were performed as described above.

[0183] Table 5 lists the catalyst compositions and N2O formation.

[0184] The result is Figure 2 As shown in the image.

[0185] Table 5: Compared with catalysts containing 2.7 wt% V₂O₅, 4.0 wt% WO₃ and 0 wt% Sb₂O₅, in A catalyst composition containing 3.6 wt% WO3 and 1.6 wt% Sb2O5 was subjected to oxidation at 550°C in both fresh and aged conditions. N2O formation varies depending on the amount of V2O5 (in weight %). .

[0186]

[0187] Implementation Plan 3: NO based on the change in WO3 quantity x Conversion and N2O formation

[0188] In a catalyst composition comprising 2.4 wt% V₂O₅ and 1.6 wt% Sb₂O₅, NO₂ varies with the amount of VWO₃ (in wt%) at 200°C under fresh and aged conditions. x Transformation shown in Figure 1In comparison, a catalyst comprising 2.7 wt% V₂O₅, 0 wt% Sb₂O₅, and a variable amount of WO₃ is also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance of 100 wt% is represented by TiO₂.

[0189] The aging of the catalyst composition and the measurement of NOx conversion were performed as described above.

[0190] Table 6 lists the catalyst compositions and NOx conversion.

[0191] The result is Figure 3 As shown in the image.

[0192] Table 6: Catalysis with 2.7 wt% V₂O₅, 1.6 wt% or 0 wt% Sb₂O₅ and variable WO₃ Compared to other catalysts, in catalyst compositions containing 2.4 wt% V₂O₅ and 1.6 wt% Sb₂O₅, the performance in both fresh and aged conditions... NO at 200℃ in a state of flux, depending on the amount of WO3 (in weight%) x Transformation

[0193]

[0194] In a catalyst composition comprising 2.4 wt% V₂O₅ and 1.6 wt% Sb₂O₅, the formation of N₂O at 550 °C under fresh and aged conditions, varying according to the amount of WO₃ (in wt%), is shown below. Figure 4 In comparison, a catalyst comprising 2.7 wt% V₂O₅, 0 wt% Sb₂O₅, and a variable amount of WO₃ is also shown. All amounts given for the respective oxides refer to the total amount of the catalyst composition. The balance of 100 wt% is represented by TiO₂.

[0195] The aging of the catalyst composition and the measurement of N2O formation were performed as described above.

[0196] Table 7 lists the catalyst compositions and N2O formation.

[0197] The result is Figure 4 As shown in the image.

[0198] Table 7: Catalysis with 2.7 wt% V₂O₅ and 1.6 wt% or 0 wt% Sb₂O₅ and variable WO₃ Compared to other catalysts, in catalyst compositions containing 2.4 wt% V₂O₅ and 1.6 wt% Sb₂O₅, the performance in both fresh and aged conditions... N2O is formed at 550°C in a state where the amount of WO3 (in weight%) varies. .

[0199]

[0200] Implementation Scheme 4: NO based on changes in Sb₂O₅ content x Conversion and N2O formation

[0201] Examples 2 and 26, which contain antimony, show higher stability and better freshness than Examples 8 and 9, which do not contain antimony.

[0202] Example 9 shows that freshness can be compensated for by increasing the tungsten content in an antimony-free formulation. However, thermal stability cannot be achieved without the addition of antimony.

[0203] Table 8 shows the NO content as a function of the amount of Sb₂O₅ for the fresh catalyst composition. x Transformation and N2O formation. NO X The result of the transformation is Figure 5 As shown in the image.

[0204] Table 9 shows the NO content as a function of the amount of Sb₂O₅ for the aged catalyst composition. x Transformation and N2O formation. NO X The result of the transformation is Figure 6 As shown in the image.

[0205] Table 8: NO variation based on the amount of Sb₂O₅ for fresh catalyst compositions 2, 8, 9, and 26 x Conversion and N2O formation

[0206]

[0207] Table 9: NO variation based on the amount of Sb₂O₅ for aged catalyst compositions 2, 8, 9, and 26 x Transformation and N2O form become

[0208]

[0209] The above embodiments demonstrate that the addition of antimony improves the thermal stability of the catalyst composition. If antimony is present in the catalyst composition, lower amounts of vanadium and tungsten are required to achieve denitrification activity within the range of catalysts containing only vanadium and tungsten but not antimony.

[0210] Contrary to existing technologies, it has been shown that WO3 is required to achieve good freshness properties in catalyst compositions, such as from... Figure 2 visible.

[0211] Implementation Scheme 5: NO content of samples containing 0% ZrO2 x Conversion and N2O formation

[0212] A water-based slurry containing TiO2 (anatase) with a dry matter content of 55% was applied to a corrugated substrate with a cpsi of 260. The zirconium-free substrate was then calcined at 580 °C. Subsequently, an impregnation solution was prepared by mixing 215 g of an water-based solution containing vanadium oxalate (7.15% V), 72 g of an aqueous solution of ammonium metatungstate (39.36% W), 151 g of deionized water, 59 g of tartaric acid, and 28 g of antimony acetate. The substrate was then immersed in the impregnation solution for 20 seconds, dried, and then heat-treated at 450 °C to produce catalytic loadings of 3.1%, 4.0%, and 1.7% %V2O5, %WO3, and %Sb2O5, respectively, based on the total weight of the catalyst composition. Sample 27 was measured under the following conditions:

[0213] NOx (250ppm), NH3 (300ppm), H2O (4%), O2 (12%), GSVH=100000h -1The balance is N2. NOx conversion was measured at 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ and 550℃.

[0214] At 550℃, H2O = (10%), and GSVH = 10000h -1 After 100 hours of aging.

[0215] The result is Figure 7 As shown in Table 10.

[0216] Table 10: NO content of fresh and aged catalyst 27 x Conversion and N2O formation

[0217]

[0218] Implementation Scheme 6: NOx Conversion and N2O Formation of Samples Prepared by One-Pot Method

[0219] A water-based slurry containing TiO2 (anatase), VO2, Sb2(glycolate)3, and WO3 with a dry matter content of 55% was applied to a corrugated substrate with a cpsi of 260, and then calcined at 580°C to produce catalytic loadings of 3.2%, 4.0%, and 2.0% %V2O5, %WO3, and %Sb2O5 based on the total weight of the catalyst composition. The sample marked 28 was measured under the following conditions:

[0220] NOx (250ppm), NH3 (300ppm), H2O (4%), O2 (12%), GSVH=100000h -1 The balance is N2. NOx conversion was measured at 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ and 550℃.

[0221] At 550℃, H2O = (10%), and GSVH = 10000h -1 After 100 hours of aging.

[0222] The result is Figure 8 As shown in Table 11.

[0223] Table 11: NO content of fresh and aged catalyst 28 x Conversion and N2O formation

[0224]

[0225] Implementation Scheme 7: Samples prepared in one pot on a cordierite substrate.

[0226] A water-based slurry containing TiO2 (anatase), VO2, WO3, and Sb2O5 with a dry matter content of 55% was applied to a cordierite substrate with a cpsi of 300, and then calcined at 580°C to produce catalytic loadings of 3.2%, 4.0%, and 2.0% of V2O5, WO3, and Sb2O5 based on the total weight of the catalyst composition.

[0227] The sample marked 29 was measured under the following conditions:

[0228] NOx (250ppm), NH3 (300ppm), H2O (4%), O2 (12%), GSVH=100000h -1 The balance is N2. NOx conversion was measured at 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ and 550℃.

[0229] At 550℃, H2O = (10%), and GSVH = 10000h -1 After 100 hours of aging.

[0230] The NOx conversion and N2O formation are comparable to those in Implementation Scheme 6.

Claims

1. A catalyst composition for the selective catalytic reduction of nitrogen oxides, said catalyst composition comprising: At least one vanadium oxide in an amount of -2.0% to 4.0% by weight, calculated as V₂O₅ and based on the total weight of the catalyst composition. -2.5% to 7.2% by weight of at least one tungsten oxide, calculated as WO3 and based on the total weight of the catalyst composition. At least one antimony oxide in an amount of -0.6% to 3.4% by weight, calculated as Sb₂O₅ and based on the total weight of the catalyst composition. At least one zirconium oxide in an amount of -0.2% to 1.0% by weight, calculated as ZrO2 and based on the total weight of the catalyst composition. - and at least one titanium oxide in an amount of 84.6% to 94.7% by weight, calculated as TiO2 and based on the total weight of the catalyst composition, The total weight ratio of the oxides of vanadium, tungsten, antimony, titanium and zirconium, calculated as V2O5, WO3, Sb2O5, TiO2 and ZrO2 respectively, reaches 100 by weight.

2. The catalyst composition according to claim 1, wherein the at least one titanium oxide is titanium dioxide (TiO2) and contains at least 95% by weight anatase.

3. An SCR catalyst article comprising a catalyst substrate, wherein the catalyst composition according to claim 1 or 2 is attached to the catalyst substrate in the form of a coating.

4. The SCR catalyst product according to claim 3, wherein the catalyst substrate is selected from corrugated substrate and cordierite solid material.

5. The SCR catalyst product according to claim 4, wherein the catalyst substrate is a solid cordierite selected from wall-flow filters and flow-through substrates.

6. A method for reducing nitrogen oxides in exhaust gas from a lean-burn internal combustion engine, the method comprising the following steps: - Add a reducing agent to the exhaust gas containing nitrogen oxides, and - The resulting mixture of exhaust gas containing nitrogen oxides and reducing agent is passed through an SCR catalyst according to any one of claims 3 to 5.

7. An exhaust gas purification system for treating diesel engine exhaust gas, the exhaust gas purification system comprising: -Oxidation catalyst, - Diesel engine particulate filter, and - The SCR catalyst according to any one of claims 3 to 5, or -Oxidation catalyst, and - A diesel particulate filter, wherein the catalyst composition according to claim 1 or 2 is present as a coating on the diesel particulate filter.

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